Incandescent electric lamp



N0. 503,770. Patented Augn ZZ, 1893.

WIT

UNiTED STATES PATENT OFFICE.

WILLIAM EMERY NICKERSON, OF CAMBRIDGE, MASSACHUSETTS.

I NCAND ESCENT "ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 503,770. dated August22, 1893.

Application filed July 3, 1893. Serial No. 479,505. (No model.)

To all whom it may concern.-

Be it known that I, WILLIAM EMERY NICK- ERSON, of Cambridge, in thecounty of Middlesex and State of Massachusetts, have invented a new anduseful Improvement in Incandescent Electric Lamps, of which thefollowing, taken in connection with the accompanying drawings, is aspecification.

My invention relates to that class of incandescent electric lamps inwhich a fusible cem cut is used for closing the neck of the bulbair-tight, more especially when the cement used, is composed wholly orin part of substances of organic origin.

The object of my invention is, in case a lamp is defective, to preventthe generation of excessive heat, by cutting out the filament from theelectric circuit when a certain temperature has been reached. Thisobject I attain by means of the device illustrated in the accompanyingdrawings, in which- Figure 1, shows in vertical section a lamp embodyingmy device. Fig. 2, shows a detail enlarged. Fig. 3, shows amodification.

In the drawings, A, Fig. 1, is the globe of an incandescent electriclamp having shoulders at A and A. The neck of the lamp is closedair-tight, and the leading-in wires supported, by the plug of fusiblecement B, which rests upon the disk 0. The disk 0 rests upon theshoulder A.

D is the filament, attached to the leadingin wires EE,E E at D D. O is aheat reflecting disk, resting upon the shoulder A, and adapted toreflect back the heat of the filament, and prevent thereby, thesoftening of thecement plug B.

R R are bodies of fusible metal, into each end of 'which,the leading-inwires E E penetrate a short distance, but do not extend entirelythrough. This construction is shown more fully in Fig. 2, which showsone of the fusible metallic bodies in vertical section, each partof theleading-in wires terminating at the points 6 6 respectively. Thesebodies are best attached to the wires by being cast upon the endsthereof. Their use, is to break the electric circuit by fusing, whenevera temperature sufficiently above the normal has been reached within thelamp, and thereby prevent the blowing out or collapsing of the lampbulb. These bodies maybe made of an alloy, consisting of tin, lead andbismuth, or other metals, in such proportion as to fuse at a temperatureof from 200 to 300 Fahrenheit or as desired. They also act incidentallyas radiators,-whereby the heat of the leading-in wires is taken up anddispersedby radiation, instead of being conducted into the cement lug.

Instead of the fusible metal section being inserted in the circuit asabove described, it may be placed on a wire ata point between the top ofthe cement plug and the brass cap by which the lamp is surmounted asshown at F Fig. 3.

If a cement which is capable of evolving a carbonaceous gas whensubjected to excessive heat, is used in closing the neck of anincandescent electric lamp bulb, the latter may under certaincircumstances become filled to a greater or less extent withcarbonaceous gases. When this occurs, the filament is built up ortreated, by the deposition of carbon upon its surface, through thedecomposition of the gases. In consequence of this much more current isallowed to pass through the lamp and an amount of heat may be produced,sufficient to liquefy the cement, allowing it to run into the lamp, oreven heat enough may be generated to soften and destroy the bulb.

'The above described action may take place,

for instance, when a lamp of the class referred to, leaks very slightlywhen new, and afterward on being put into operation becomes tight. Theaction then may be as follows:--The small amount of air which has leakedinto the lamp causes it, by convection and otherwise, to become hot. Theabnormal amountof heat thus generated, softens the cement and allows itto close up the original leak. If the heat has been sufficient to allowa small portion of the cement to flow into the lamp, or to generate gas,then a treating or building up of the filament takes place, Whereby itscross section is increased and its resistancediminished. An increasedamount of current is thus allowed to flow through the filament, whichstill further raises the temperature of the lamp, generating more gas,which in turn further builds upthe filament, allowing still more currentto pass, and so on until the lamp may attain a temperaturesufficient'lyhigh to fuse the cement and allow it to run into the'lamp,or to soften the glass of the bulb, either causing it to blow out orcollapse, according as the pressure of thegas within the lamp, isgreater or less than that metal in the circuit as described, whereby theelectric current is cut offby the melting of said metal, if the lampbecomes overheated, substantially as and for the purpose set forth.

2. In an incandescent electric lamp, the

combination of a glass globe A having a neck of the temperature.

The gist of my invention consists in placin g in circuit on theleading-in wires of a'nincandescent lamp, a section of a fusible metal,whereby the current will be cut 05 by the fusion of. this metal, beforea temperature sufficiently high has been reached within the lamp, toblow out or collapse the bulb, when from any cause gas or air hasdestroyed the vacuum in the lamp globe.

' I (-1ai-m- '1. In an incandescent electric lamp, in which the-neckofthelamp bulb is closed'a-i'rtight by a'fusible-cement, a section offusible f.

adapted to be sealed air-tight by a fusible cement, filament D,leading-in wires E E, E E ,cemeut plug B, andsection of fusible metal Rin circuit, adapted to melt and break said circuit if the lamp becomesoverheated, substantially as and for the purpose set forth.

In testimony whereof I have signed my name to this'specification, in thepresence of two subscribing witnesses, on this 1st day of July, A. D.1893.

WILLIAM EMERY NIGKERS'ON Witnesses-z FRANK G: PARKER,-

EDWARDS. DAY;

